Photoredox Promoted Barbier-Type Reaction of Alkyl Iodides with N-Alkyl and N-Aryl Imines

Abstract

The reaction of organozinc reagents with unactivated imines is accelerated when performed in the presence of a photocatalyst under blue light irradiation. Coordination between Lewis acidic zinc iodide and the imine is a key factor responsible for the reaction efficiency. The method can be carried out using alkyl iodides under Barbier conditions.

Mannich‐Type Reactions of Alkylzinc Reagents

“…The use of less electrophilic imines bearing a 2‐pyridylsulfonyl electron‐withdrawing group on the nitrogen atom has also been described, but the use of an additional copper catalyst is essential to increase the electrophilicity of the carbon atom [25] . More recently, reductive couplings between alkyl halides and N ‐aryl or N ‐alkyl aldimines have been described, but these transformations also rely on the use of transition metal catalyst in combination with a stoichiometric reductant [26–28] . In continuation with our work on organometallic Mannich reactions using alkylzinc halide reagents, [29] we report, in this comprehensive study, the development of Mannich‐type reactions involving unactivated organozinc reagents and aldimines.…”

“…[25] More recently, reductive couplings between alkyl halides and N-aryl or N-alkyl aldimines have been described, but these transformations also rely on the use of transition metal catalyst in combination with a stoichiometric reductant. [26][27][28] In continuation with our work on organometallic Mannich reactions using alkylzinc halide reagents, [29] we report, in this comprehensive study, the development of Mannich-type reactions involving unactivated organozinc reagents and aldimines.…”

BF2‐Chelates of N‐Acylhydrazones as Versatile Coupling Partners in Photoredox Promoted Reactions

“…Since alkyl radicals are considered to have nucleophilic character, [17,18] their addition may proceed faster if the azomethine substrate either has an electron withdrawing substituent or is activated by Lewis acids. For example, the latter concept has recently been successfully used in Lewis acidic activation of otherwise unreactive N-alkyl imines [19] (Scheme 1A). Another approach involves intramolecular Lewis acidic activation, that is the formation of chelate complexes.…”

Syntheses, characterizations and catalytic properties of three zinc complexes and one lithium compound chelated by β-diketiminate ligands

“…[1][2][3][4][5][6][7] In addition to the aesthetically pleasing topologies that many zinc complexes display, interest in these compounds also comes from their versatile reactivity, [8][9][10][11][12][13] including but not limited to the hydroboration of alkynes [14][15][16] and various polymerizations. [17][18][19] These compounds can be used in the Barbier reaction [20][21][22] and Strecker reaction. 23,24 Recently, they were employed in the hydrosilylation of N-heterocycles 25,26 and aminophenol oxidation.…”